SS · stainless
Stainless Steel 17-4 PH (630)
In the annealed condition it machines like a tough 304; in H900 it is hard enough that finishing has to be done by grinding or hard turning.
Quoting this material
- Typical lead time
- 10–15 working days
- Condition
- Condition A (annealed) or aged to H900 / H1025 / H1075 / H1150
- Achievable finish
- Ra 1.6 µm annealed typical · Ra 0.4 µm best
Machined in-house to your drawing: see the precision CNC machining service and the machine and inspection capability it runs on.
Machinability
Our own 1–10 shop ranking, not a published index: 10 is free-cutting brass C360, 1 is Inconel 718. It ranks how a material behaves on the floor - cycle time, chip control and tool life together. Where a published index exists it is quoted in the note.
In the annealed condition it machines like a tough 304; in H900 it is hard enough that finishing has to be done by grinding or hard turning.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength (H900) | 1,310 | MPa |
| Yield strength (H900) | 1,170 | MPa |
| Elongation (H900) | 10 | % |
| Hardness (H900) | 44 | HRC |
| Thermal conductivity | 18.4 | W/m·K |
| Modulus of elasticity | 197 | GPa |
Hardness, tensile and thermal figures are typical published values for the condition stated. Actual mill certificates govern; send the specification with the drawing and we confirm against the certificate before the material is cut.
Condition
Condition A (annealed) or aged to H900 / H1025 / H1075 / H1150
Heat treatment
Precipitation hardening, and it works properly in the shop: machine in the annealed condition, then age to the required condition. H900 gives the highest strength at 44 HRC, H1150 the highest toughness at around 30 HRC. Distortion is modest but real, so critical dimensions are finished after ageing.
Achievable surface finish
Ra 1.6 µm annealed
Ra 0.4 µm
Finishing after ageing is a grind or hard-turn operation; passivation is normal afterwards for corrosion-critical parts.
Tooling and cutting parameters
Cutting speed
- 120–200 m/min annealed (carbide) · 60–90 m/min at 44 HRC (ceramic or CBN)
Feed
- 0.10–0.25 mm/rev turning · 0.06–0.15 mm/tooth milling
Tooling
- Coated carbide annealed; CBN or ceramic inserts for the aged condition
Coolant
- Flood, and never dry on the aged material
Starting points for carbide on a rigid setup, not a guarantee. The right numbers depend on the machine, the toolholder and the fixturing - ask and we will say what we would actually run.
Typical applications
- Valve stems and high-pressure fittings
- Aerospace structural fasteners
- Chemical process pump shafts
- Medical instrument components
- Turbine and compressor hardware
DFM notes for this grade
- Decide the ageing condition before the part is drawn: H900 and H1150 machine, grind and behave differently, and the finish allowance follows from that choice
- Ageing moves the part - leave stock on any tolerance below 0.05 mm and finish after heat treatment
- Excellent corrosion resistance but it is not 316L: in strong chlorides and sour service, check the specification rather than assuming
Questions buyers ask
- Should the part be machined before or after ageing?
- Almost always before, then finish after. Annealed 17-4 cuts like a tough stainless; at 44 HRC it needs CBN or ceramic and everything takes longer. The sequence is rough in the annealed state, age, then finish the critical features with the material hard and stable.
- Is 17-4 PH always the answer for a strong stainless part?
- It is the standard one because it is available in bar, it ages at a modest temperature (around 480–620 °C depending on condition) and the distortion is manageable. Where higher toughness is needed, 15-5 PH is the same family with fewer delta-ferrite issues on a large section.